Potato chips have been enjoyed as a typical popular snack food. As potato chips, real potato chips obtainable by slicing and frying potatoes, and fabricated potato chips obtainable by shaping a dough which contains a dried potato such as potato flakes or potato powder as a main material, into a sheet-like configuration, and then frying it or baking it by an oven, have been known.
On the other hand, in recent years, snack foods containing a little fat and oil, have attracted attention. In producing such low fat snacks, it is easier to produce them by putting an oil on baked or puffed ones, rather than frying. Potato chips have been usually produced by frying. However, in the U.S.A. or the like, fabricated potato chips which contain a little fat and oil, obtainable by baking by an oven, have been produced.
FIG. 7 is a diagrammatic view of an oven for baking sheet-like doughs. In this figure, 1 is a steel band conveyer or a mesh band conveyer, and 2 is an oven body having heaters 3 disposed at the upper and lower portions of the conveyer 1. The dough 4 is placed on the conveyer 1 and introduced into the oven body 2, then baked by heaters 3 disposed at the upper and lower portions of the conveyer 1, and taken out.
However, when a sheet-like dough which contains a dried potato as a main material, is baked by an oven having a steel band conveyer, the following problems have been pointed out.
Namely, in FIG. 8, 5 is a steel band, and 4 is a sheet-like dough baked thereon. When a shaped dough is baked on a steel band 5, air remains between the dough 4 and the band 5, and the air does not run out during the baking and is expanded by heating, thereby partially raising the dough 4. Since the partially raised portion 4a is away from the band 5, heat conduction is remarkably poor, the moisture is hardly removed and the color turns white. Further, this partially raised portion 4a is susceptible to cracking. Furthermore, if the dough is baked until the moisture in the partially raised portion 4a is completely removed, other portions will be burnt. Accordingly, in any case, there is a problem that the market value becomes remarkably low.
Further, when a sheet-like dough containing a dried potato as a main material, is baked by an oven having a mesh band conveyer, there have been the following problems.
Namely, a film through which moisture hardly permeates, is formed on the surface of a sheet-like dough during the baking, and the moisture evaporated in the dough can not run out, and as shown in FIG. 9, baked fabricated chips 6 are partially hollowed, whereby blisters 6a are formed. Since the blisters 6a are formed random in various sizes, the appearance becomes bad, uniform products can not be produced, and the strength becomes remarkably low.
In order to solve such problems, there have been known products obtained by making pinholes on a sheet in a predetermined interval, and baking it while removing the air through the pinholes. Namely, in the case of using a steel band, the air between the dough and the steel band is removed through the pinholes to prevent the partial raising, and in the case of using a mesh band, the moisture evaporated in the dough is allowed to run out through the pinholes to prevent the formation of hollowed products.
However, to obtain the above effects sufficiently, it is necessary to form a lot of pinholes, and as a result, the product has an appearance with incongruity as a snack food, and the strength deteriorates, such being problematic. For example, with fabricated potato chips produced in the U.S.A. by use of an oven, since pinholes formed thereon, somewhat incongruity is felt as a snack and a number of cracking are seen.